What is shot blasting?

Shot blasting is a popular choice in the steel fabrication industry, utilised to ensure that steel is free contaminants and ready for further treatment.

In this month's Galvanizing Today article, we explore what shot blasting, is and why it is important when it comes to protecting steel.

Shot blasting explained

Shot blasting?is a process to remove paint, oils, and other substances from the surface of steel.

The shot blasting process uses small amounts of materials known as "shot". Commonly, materials such as aluminium oxide or carbon grit are propelled onto the steel at high speed. Shot blasters can use many different types of material as "shot".

Shot blasting is predominantly used to prepare steel for a further process such as hot dip galvanizing. It can also be used to blast black steel to help generate a thicker coating when it is time to hot dip galvanize it. It should be note that shot blasting is different to sand blasting.

Why shot blast steel?

Steel cleanliness is vital for ensuring an effective hot dip galvanizing and powder coating application. Shot blasting is an effective way of removing surface contamination that would otherwise not be removed by the typical chemical pre-treatment used in both galvanizing and powder coating facilities (i.e. paints, waxes or heavy oils). The zinc from the galvanizing bath cannot bond to the steel effectively if there is residue preventing it from making contact with the steel surface. Powder coating also becomes affected, impacting the end quality and reducing the coating's lifespan and durability.

As a rule, surfaces with a roughened finish, such as steel which has been blasted, form thicker coatings during hot dip galvanizing than usual. This is because the rough texture of the surface creates a larger surface area for the molten zinc to react with. Increased coating thickness helps contribute to its longevity, protecting the underlying steel against corrosion for longer. This process is typically used for articles that are required to withstand a usable life in a harsher, more corrosive environment, for example, in coastal regions.

Since the process is surface-level, it avoids chemically altering the fabrication. It's also a quick process thanks to the speed the shot is sprayed at.

Finally, shot blasting is an environmentally friendly process; metallic shot can be re-used multiple times, reducing material costs and excess waste.

Shot blasting at Joseph Ash Galvanizing

Joseph Ash Medway is home to our specialist shot blasting facility. Based in Kent, the site offers a one-stop shop facility of steel treatment and protection services, including hot dip galvanizing and powder coating. The site also offers collection and delivery services across the South East and surrounding areas, so you can save money and time arranging work from multiple companies. Our cabinets are fully approved and meet all health and safety, and environmental regulations.

Have you learnt something new about shot blasting? Let us know in the comments.